Degradation profile oxidation

Incorporation of a 2% level of either ZnSn(OH) or ZnSnO into the resin, leads to marked differences in its thermal degradation profile. The initial decomposition comprises two distinct stages, the major step occurring at a lower temperature than that of the untreated polymer, which may be indicative of promotion of bromine volatilisation by the zinc stannates. Furthermore, the amount of residue burnt off in the char oxidation step is greatly increased in the tin-containing samples, and the temperature at which this process occurs is significantly higher than in the base resin. 

Recently, the reaction between the sulfate radical anion and cyanuric acid, a nondegrad-able end product of the oxidative degradation of the triazine-based herbicide-atrazine, was reported. The degradation profile indicates that about 76% of the cyanuric acid has been decomposed after an absorbed y-radiation dose. It is therefore proposed that the reaction of peroxydisulfate could be utilized for the degradation of cyanuric acid in aqueous medium, which is important, since the latter is normally stable to further organic processes. 

It is common practice to utilize forced degradation studies to accelerate degradation of the drug substance or drug product to get an understanding of its degradation profile. Potential environmental conditions that can be used include 40°C and 75% relative humidity (RH), 50°C and 75% RH, 70°C and 75% RH, or 80°C and 75% RH. Oxidation, reduction, and pH-related degradations are... 

Within various types of the family of plastics (PE, PVC, PP, etc.) each type usually have different heat profiles and other settings (Table 5.1). Experience shows how to set the profile and/or obtain preliminary information from the material supplier. Degrading or oxidizing certain plastics is a potential hazard that occurs particularly when the extruder is subject to frequent shutdowns. In this respect, the shutdown period is even more critical than the startup period. 

To establish the degradation profile of a new drug, forced or stressed conditions such as hydrolysis, oxidation, photodegradation, and solid thermal decomposition are applied to the drug to generate degradation products that may be monitored by TLC or HPLC. 

The visual rings seen in cross-sectioned, polished samples correspond to areas having large differences in the extent of oxidation, and are useful for identification of heterogeneous degradation and for a qualitative or semiquantitative determination of the depth of oxidation. However, the exact shape of the degradation profile... 

It was concluded that this overall increase in efficiency is essentially because of thermal enhancement of subsequent oxidation reactions of the primary photoreaction intermediates. Optimization revealed that this effect is particularly significant for samples containing low concentrations of H2O2, although a large excess of H2O2 was essential for complete destruction in most experiments. The degradation profiles of the techniques used in the destruction of 4-chlorophenol are com-... 

As can be seen, there is no difference in the thermal degradation profile from dry to humid air. On the other hand, the ehmination of the carbonaceous residue occurs at lower temperatures in oxidizing atmospheres than in an inert one (N2). Furthermore, it can be seen that ascorbic acid is stable until almost 200°C. The visual observation performed in an electric furnace of the thermal degradation residues at 190°C, 220°C, and 240°C shows that they exhibit characteristics typical of fired sugar [16]. Furthermore, the infrared spectra obtained for each residue shows that they... 

In products with a large wall thickness, the influence of weathering is often limited to a surface layer, either due to limited oxygen diffusion or to limited UV penetration. The depth of this layer may be small ( 0.5 mm) compared with the whole wall thickness ( 4 mm) but it can causes brittle fracture. Mechanical behavior depends on the oxidation (degradation) profile, a critical degradation profile accounted for the failure of samples, that is time of failure. Tensile tests were performed on films microtomed from the samples [39]. The density of weathered samples can increase because of chemicrystallization, increase in polar groups, oxygen uptake or the loss in volatile products. The decrease in the nominal strain corresponded to an increase in the vinyl index and in the density. The carbonyl index showed too much scatter. 

Subambient thermal volatilization analysis can also be used to probe the effects of physical fillers in silicone materials. In 2008 Lewicki et al. [51] studied the degradation profiles and product speciation of a series of montmorillonite clay filled silicone elastomers which had been characterized using SATVA. Shown in Figure 13.17 are a series of TVA thermal degradation profiles for the non-oxidative degradation of a bimodal-condensation-cured silicone matrix, filled with 0-8 wt% of organically modified montmorillonite (0-MMT) exfoliated nanoclay platelets. 

DBCP. The predictions suggest that DBCP is volatile and diffuses rapidly into the atmosphere and that it is also readily leached into the soil profile. In the model soil, its volatilization half-life was only 1.2 days when it was assumed to be evenly distributed into the top 10 cm of soil. However, DBCP could be leached as much as 50 cm deep by only 25 cm of water, and at this depth diffusion to the surface would be slow. From the literature study of transformation processes, we found no clear evidence for rapid oxidation or hydrolysis. Photolysis would not occur below the soil surface. No useable data for estimating biodegradation rates were found although Castro and Belser (28) showed that biodegradation did occur. The rate was assumed to be slow because all halogenated hydrocarbons degrade slowly. DBCP was therefore assumed to be persistent. 

Figure 2 Relative concentration profiles of oxidation products during thermal degradation as a function of depth for a plaque with thickness 3 mm Nearly homogeneous profile when the degradation depth, a, is 3.0 mm, similar to sample thickness, and heterogeneous profile when the degradation depth, a, is 0.1 mm, smaller than the sample thickness. The profiles were calculated from Equation (4).

---